Rheological Properties of Starch and Whey Protein Isolate Gels

Abstract

The paste viscosity of starches Amioca (~0.5% amylose), native corn (~27% amylose), Hylon VII (~70% amylose), tapioca (~19% amylose), and their whey protein isolate (WPI; 50/50) mixtures at varying solid concentration of 2.5, 5, 10, 15 and 20% were determined. At higher gel concentration (20%) during the cooling cycle, WPI paste measured by rapid visco-analyser (RVA) showed a tremendous increase in viscosity over that of the micro visco-amylograph (MVA), 5784 and 184 cP, respectively. RVA gels had a more uniform network of coarse particles (~250—500 nm) than the fine structures (~50 nm) in those of the MVA. Inclusion of WPI reduced the paste viscosity of all starches by at least 50%, except for Hylon VII at 20% solid concentration. The strength of Hylon VII and corn starch gels was reduced by WPI. In contrast, gels of WPI/tapioca ( G' = 45.4 Pa) and WPI/amioca ( G' = 18.3 Pa) had similar rheological properties as their pure starch control ( G' = 47.4 Pa and G' = 15.3 Pa for Tapioca and Amioca, respectively).